Method of releasably adhering sponge backed carpet to floor surfaces and adhesive used therefor



United States Patent US. Cl. 15671 3 Claims ABSTRACT OF THE DISCLOSURESponge backed carpet and carpeting is releasably adhered to a variety offloor surfaces by a particular syn thetic latex adhesive based oncopolymer of Z-ethylhexyl acrylate and N-tertiary-butylacrylamide.

This invention is concerned with a method for adhering sponge backedcarpets and carpeting to various types of floor surfaces. It is moreparticularly concerned with providing a method of adhering carpeting toa floor surface whereby the carpeting will not shift in use, yet canreadily be lifted and then relaid in the same or different positionwithout the addition of further adhesive.

In modern office buildings, schools, motels, private homes and the likethere is a trend to the use of fabric carpeting, particularly wall toWall carpeting for floor coverings. Carpeting is generally more pleasingto the eye and comfortable to the foot than uncovered wood, resilienttile, terrazzo, cement, and the like. Though initially more expensive toinstall than other types of floor covering, carpeting is much lesscostly to clean and maintain. It is desirable, however, that thecarpeting, once laid, not shift, creep, crawl and bunch up under theshifting of furniture and heavy loads passing across it or from thetraffic of countless feet.

In homes, carpeting is normally nailed down to prevent such shi-fting.This act of nailing, however, sets up the difficult task of nailremoving when and if the carpet is to be lifted for cleaning, turning toeven the wear, or for any other reason. Tackless carpeting techniquesare available and require the services of a skilled carpet layer as thecarpet must be stretched over forms and fastened.

Most carpeting is laid with a pad of fabric, rubber, or the like,underneath it to serve as a cushion and shock absorber. Paddingcontributes to the comfort of walking on the carpet and to the wearlifeof the carpet. A recent trend, particularly in commercial locations, isto use a combined carpeting and padding by employing a sponge backedcarpeting construction. This material saves a large portion of the laborcost incurred in laying separate padding and carpeting. The spongebacking may be based on natural rubber latex, polyurethanes, orstyrene-butadiene rubber latex. The adhesives of this invention arecompatible with all classes of rubber sponge.

Carpeting and padding may be fastened to wood floors or through a woodedge molding, by conventional nailing techniques. Removal, however,requires removal of both the molding and the nails and holes arenecessarily punched into the carpet by the nail. Where no wood floor ormolding is available for nailing, the padding and carpet are laid as iswith only the fraction force between floor and padding and padding andcarpeting to hold the installation in place. Carpeting installed in thismanner is 3,442,731 Patented May 6, 1969 "ice readily lifted forcleaning, turning, or any other purposes but tends to shift out ofposition and bunch up when heavy loads such as baggage or furniture areshifted across it. If the carpet has been installed by the t'acklesstechnique, the services of the carpet layer will again be required toplace the carpet down in proper fashion.

Attempts have been made to employ adhesives to secure the sponge backedcarpeting to various flooring surfaces, but to date no satisfactoryadhesive has been found. An adhesive with too much strength contributesto destruction of the sponge backing or even the floor surface when thecarpet is lifted; an adhesive that is too weak is not satisfactory inholding the carpeting in place under the shifting of loads, as whenfurniture is pushed from place to place when cleaning or rearranging theroom appearance.

Quite by chance, there has now been found a particular family ofadhesive copolymers that can be applied in thin coats to continuousflooring of any nature, wood, vinyl or rubber or asphalt tile, concrete,marble or metal, or to a sponge-backed carpeting, or to both the surfaceof said flooring and of said sponge-backed carpeting, whereby the saidcarpeting, once cut to the desired size and shape, can be laid in thedesired spot, smoothed down, and will remain flat in the selected spotor area under trafiic of feet, wheeled trucks carrying baggage orfurniture and the like, or the push shifting of heavy items of furnitureand the like directly across the surface of the carpet itself. Thecarpet will not bunch or shift. Furthermore, after any period of timedesired, either hours, days, months or years, the adhesive releases witha slight lifting force and the carpet can be lifted readily, shifted forany desired purpose, then relaid in the original, reversed, or any otherdesired configuration in the same room or pl-ace or in another room,without the requirement for adding any further adhesive to the carpetsponge backing. After such reinstallation-s, the carpeting has the sameresistance to bunching or shifting that it had previously. If the carpetis properly cut to size no special skills or talents are required toperform a proper job of laying it.

The adhesive which exhibits the remarkable property of adheringsponge-backed carpeting to any conventional floor surface for as long aperiod of time as may be desired, then permits ready removal of thecarpet without any destruction of the backing thereof, andreinstallation of said carpeting, is a family of emulsion copolymers ofZ-ethylhexyl acrylate and N-tertiary-butylacrylamide. These are bothcommercially available monomeric materials.

It is surprising that only N-tertiary-butylacrylamide and Z-ethylhexylacrylate combine to form a permanently tacky releasable adhesive. Whenlower and higher alkyl acrylates and methacrylates are substituted for2-ethylhexyl acrylate or another acrylamide monomer is substituted forN-tertiary-butylacrylamide non-tacky, unstable latices result which donot have the adhesive properties of the particular combination of theinvention.

The 2-ethylhexyl acrylate is readily copolymerized in an aqueousemulsion system with N-tertiary-butylacrylamide to complete conversionin ratios of 99.9/ 0.1 to 50/50 weight percentacrylate/N-tertiary-butylacrylamide. While copolymers of 50 parts andeven higher N-tertiary-butylacrylamide can be made, the preferred rangeof the acrylamide is 10 parts and "below, and the most preferred rangeof N-tertiary-butylacrylamide in the adhesive copolymer is 5.0 to 7.5parts per parts of copolymer.

A typical recipe for emulsion copolymerization of the copolymers is asfollows:

Material: Parts Z-ethylhexyl acrylate 90-999 N-tertiary-butylacrylamide0.1 Water 150 Decyl benzene sodium sulfonate 0.9 Condensation product offormaldehyde and naphthalene sulfonic acids 1.0 Sodium pyrophospha-te0.5 Potassium persulfate 0.1

Water is charged to a glasslined polymerizer which is purged andpressured with nitrogen. Soaps and emulsifiers are added, followed bythe monomers. The polymerizer is evacuated and purged with nitrogen;then the persulfate catalyst is added and the temperature is raised to50 C. The polymerization runs to complete conversion in approximatelyhours at 50 C. The copolymer latex is usable directly as drawn from thepolymerizer in the practice of this invention. Latex total solids runsabout -55% by weight, with to being preferred.

Adhesives of this invention are evaluated in a laboratory peel test anda laboratory tack test. In the peel test a 1" x 6" strip of spongecarpet backing is brush coated with a layer of test adhesive. When theadhesive layer is dry to the touch, the strip is pressure bonded by twopassages of a four pound roller to a panel of standard resilient floortile which may be rubber, vinyl, or asphalt. The test panels are allowedto stand under no pressure for 48 hours. The test strip is then peeledback at 180 at a rate of 2" per minute and the force required to peel isregistered as lbs. per inch of strip width.

The tack test is performed on a laboratory-constructed tackmeter. Thisis a simple triple beam balance suspended 10 inches above a scissorsjack A cylindrical metal rod, eight inches long, with one end ground toa pencil-like one-sixteenth inch diameter point, is suspended from thebalance pan. Test adhesive films are prepared by putting a known volumeof test adhesive into exactly similar shaped open cup molds and ovendrying the films at 100 C. Each test film is placed in contact at itscenter point with the contact rod of the tack-meter by raising the filmin its mold up to the contact rod on the jack. Contact is maintainedwith no increase in pressure for a standard length of time seconds issufficient). Polymers from which the films are made for the test musthave percent total solids in the same general range, plus or minus 5%.After a contact time of one minute, onehalf gram weights are added tothe balance at uniform time intervals (usually 5 seconds) untilsufficient weight causes the contact rod to break loose from the tacky,dried polymer film. This weight has to overcome only the films tackwhich, after subtracting the tare weight of contact rod, is a directmeasurement of tack and is easily converted to gms./sq.cn1, of force.Each film is prepared and tested in the same manner.

The following examples will serve to illustrate the invention.

EXAMPLE I The following recipe is charged to a 15 gallon glasspoly'merizerr Z-ethylhexyl acrylate N-t-butylacrylamide 10 Water Decylbenzene sodium sulfonate 0.9 Cond. product of formaldehyde andnaphthalene sulfonic acids 1.0 Sodium pyrophosphate 0.5 Potassiumpersulfate 0.1

One hundred twenty-five parts of water are charged, heated to 60 C. andevacuated until boiling. The polymerizer is pressured with nitrogen andcooled to 25 C.

Soaps and pyrophosphate are added, followed by the monomers. Thepolymerizer is purged with nitrogen and the potassium persulfate,dissolved in the balance of the water, is pressured into the charge. Thepolymerizer is heated to 50 C. and run to complete conversion in 30hours. The final latex, marked A, has a total solids of 39.4%, Whentested as an adhesive, latex A registers 20 oz. per inch width in thepeel test and 580 gm./sq.cm. in the laboratory tack tests. Tack testsare run in duplicate and the results are averaged. Similarpolymerizations are run with the following charging ratios and testresults.

Z-ethylhcxyl acrylate/N-tert. Peel test, Tack test, butylacrylamide0z./in. width gm./sq. cm.

When the peel test and tack test results are plotted versus percentN-tert.-butylacrylamide charged, the range of maximum adhesion is foundto occur when 5 to 7.5 parts are used.

When N-methylolacrylamide is substituted for N-tertiary-butylacrylamide,the latex produced is unstable. When ethyl acrylate and laurylmethacrcylate are substituted for 2-e'thylhexyl acrylate, the laticesare non-tacky and do not form an adhesive.

EXAMPLE II The 2-ethylhexyl aerylate/N-tertiary-butylacrylamide latex ofRun A, Example I, was applied with a short fiber (mohair) paint typeroller to the natural rubber sponge backing of 20 square yards (10 yds.2 yds.) of a commercial grade carpet. Half the length of carpet was laidover concrete floor; half the length over asphalt tile floor. The floorwas not cleaned before the test.

The cemented carpet was laid out in the chosen position in a heavilytraveled hallway by merely unrolling it in place and pressing down theends by hand. The carpet was subjected to heavy morning, midday andevening foot traffic and constant light foot traffic during the workday. Ofiice and laboratory hand trucks carrying ice, gas cylinders,laboratory supplies and mail crossed it daily.

In one month, the carpet, which was rimmed by open floor on all sides,had not shifted or bunched under any of the trafiic load applied. After30 days the carpet was easily rolled up. The removal did not cause anytearing in the sponge backing of the carpet.

The floor was then cleaned by the building maintenance floor cleaningmachine using detergent and hot water. The rolled up carpet was allowedto stand for 3 days; then was unrolled in place again and observed for 3more days under the same trafiic as before, The tacky adhesive held thestrip firmly in place and was still tacky to the touch when the teststrip was again rolled up and stored.

I claim:

1. The method of releasably adhering sponge-backed carpet to a floorsurface comprising spreading on the said floor surface and/or the saidsponge backing surface of said carpet an adhesive layer of a syntheticlatex comprising a 35% to 55% total solids copolymer of 99.5- 90-0 partsby weight 2-ethylhexyl acrcylate and 0.5-10.0 parts by weightN-terti-ary-butylacrylamide.

2. The method of releasably adhering sponge-backed carpet to a floorsurface comprising spreading on the said floor surface and on saidsponge-backing surface of said carpet an adhesive latex which comprises0.5-10 parts by weight N-tertiary-butylacrylamide and 99.5-90 parts byweight 2-ethylhexyl acrylate.

5 6 3. A permanently tacky, releasable adhesive compris- 3,014,829 12/1961 Curtin 156-71 X ing a copolymer of 0.5-10.0 parts by weightN-tertiary- 3,135,647 6/1964 Wheeley 156-71 X butylacryl-gmide and99.5-90.0 parts by weight Z-echyl- 3,157,562 11/1964 Kine et a1. 161-170hexyl acryl-ate. 3,248,260 4/ 1966 Cangerak et a1 117-161 ReferencesCited 5 3,332,827 7/1967 Griffith et a1. 156-71 X UNITED STATES PATENTSHAROLD ANSHER, Primary Examiner. 2,541,465 2/1951 Dickey 260-861 X U SC1 XR 2,761,856 9/1956 Suen et a1. 260-861 X 2,808,388 10/ 1957Hellm'ann 260-8 156-332, 247; 260-861, 29.6

UNITED STATES PATENT OFFICE 56g PGERTIFICATE 0F CORRECTION Patent No3,1m2,731 Dated y 969 Inventofli) J6EE F. ANDERSON It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

I /T 101m 1, line 59 "carpeting" shofild be --carpet-- line 66, .1

"fraction" should be --friction--.

column 6, line t "Cangersk et 81" should be --Langerak et al-- SIGNEDAND SEALED APR 7 4970 Atlas: 4

i E. SW, JR- I. l fis ifiioner of Pawn

